Sampling risk is the possibility that the items selected in a sample are not truly representative of the population being tested. This is a major issue, since an auditor does not have the time to examine an entire population and so must rely upon a sample. One error that can arise from sampling risk is that the auditor erroneously concludes that there are fewer problems with the population than expected, which can lead to an incorrect audit opinion. Or, the auditor erroneously concludes that there are more problems than expected, and so expands the sample size to see if this is really the case, which is not a good use of his time.